| 
           Property and Equipment, Net of Accumulated Depreciation (Details) (USD $) 
        In Millions, unless otherwise specified  | 
        3 Months Ended | ||
|---|---|---|---|
| 
           Aug. 31, 2012 
         | 
        
           Aug. 31, 2011 
         | 
        
           May 31, 2012 
         | 
      |
| Components of property and equipment, at cost | |||
| Land and improvements | $ 7.3 | $ 7.0 | |
| Buildings and improvements | 97.8 | 96.8 | |
| Data processing equipment | 175.6 | 212.3 | |
| Software | 279.7 | 263.5 | |
| Furniture, fixtures, and equipment | 154.4 | 154.2 | |
| Leasehold improvements | 96.6 | 96.0 | |
| Construction in progress | 20.1 | 28.2 | |
| Total property and equipment, gross | 831.5 | 858.0 | |
| Less: Accumulated depreciation and amortization | 504.6 | 533.7 | |
| Property and equipment, net of accumulated depreciation | 326.9 | 324.3 | |
| Property and Equipment, Net of Accumulated Depreciation (Textual) [Abstract] | |||
| Depreciation expense | $ 19.4 | $ 18.5 | |
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- Definition 
          Data processing equipment gross. No definition available. 
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- Definition 
          Furniture fixtures and equipment gross. No definition available. 
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- Details 
          
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- Definition 
          The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Amount before accumulated depreciation of building structures held for productive use including addition, improvement, or renovation to the structure, including, but not limited to, interior masonry, interior flooring, electrical, and plumbing. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          The gross amount of capitalized computer software costs as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Gross amount, at the balance sheet date, of long-lived assets under construction that include construction costs to date on capital projects that have not been completed and assets being constructed that are not ready to be placed into service. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Carrying amount of real estate held for productive use and alterations to land which improves its potential for use, examples include, but are not limited to, walkways, driveways, fences, and parking lots. Excludes land held for sale. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Gross amount, at the balance sheet date, of long-lived, depreciable assets that are an addition or improvement to assets held under lease arrangement. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
          
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